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    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> 
    <title>第七课 运算符</title>
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    <script>
        // var a = 10;
        // var x = 30;
        // var y = 0;
        // var z = 0;
        // y = z = x;
        // alert(x);
        // alert(y);
        // alert(z);
        // var a = 10;
        // // a = a + 5;
        // a += 5;
        // alert(a);
        // var a = 5;
        var a;
        123
        a > 0
        a > 1 && a > 3
        true
        'helloxingxingketang'
        Math.PI
        a = 100 + 10 / 3;
        typeof a
    </script>                      
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